Knee ligament balancing is necessary for long term successful total knee function. Valgus and varus knee arthritis is associated with variable degrees of ligament contracture on the worn side and attenuation or laxity of the ligaments on the opposite compartment. If not addressed either limb mal-alignment or knee instability is expected. Therefore ligament lengthening or release should be performed in most total knee procedures. Problems with ligament imbalance are known to lead to accelerated poly wear, pain instability and stiffness.
Currently no consensus exists regarding the best method to produce a balanced knee. Many differing techniques and sequences for ligament release have been reported over the years. New tools have been introduced to help the surgeon; for example, computer-assisted surgery and tensor balancers. However, randomized control trials comparing different techniques, sequences, and tools are limited. The best method of achieving the balanced knee is yet to be determined.
In one example of an arthritic knee, the worn lateral side has a tight collateral ligament while the superficial medial collateral ligament on the less worn side is too loose. With reference to FIG. 1, in addition to any cartilage damage on the condyles, the knee is misaligned such that the lateral ligament LL is too short or tight, while medial ligament ML is too long or lax to properly maintain the alignment of the knee. As shown, the joint 10 between the femur F and the tibia T is misaligned.
Referring to FIG. 2, the knee joint of FIG. 1 is illustrated with prosthetic knee components 12 and 14 positioned in the joint. Utilizing a prior art technique, pie cuts 16 are made in the lateral ligament LL to lengthen the ligament to attempt to achieve re-alignment of the knee joint. However, as shown this technique does not address the laxity of medial ligament ML. Moreover, the cuts in the LL ligament tend to weaken the ligament which may lead to rupture.
Referring to FIGS. 3A-3C, a technique is illustrated for shortening the medial ligament ML by cutting out a bone block 20 with attached ligament, removing cancellous bone with instrument 24, and recessing the medial collateral ligament origin into the metaphyseal bone opening 22 of the femur. The bone block 20 may be held in place by suture 26 extending through the femur.
Methods of knee ligament balancing are still controversial and there remains a need for improvement devices and methods for obtaining a balanced knee.